The present invention relates to an intraocular implant for correction of aphakia, comprising a substantially circular optical part made of a first flexible material allowing it to be folded along a diameter, and a haptic part.
Intraocular implants constitute an optical system correcting the vision of the human eye which may, in a certain number of cases, replace corneal lenses or external corrector lenses. An intraocular implant is essentially composed of an optical part of generally circular or slightly ovalized shape which constitutes the optical corrector system proper, and by a haptic part which serves to position, fix and maintain the optical part in collect position inside the eye.
New operating techniques wake it possible to reduce the incision made in the eye. For example, in the case of the operation for cataract, the so-called phako-emulsification operating technique allows the ablation of the opaque lens by the introduction in the eye of an ultrasound probe presenting a system of irrigation/suction. By the combined action of the ultrasounds and of the flux of balanced saline solution, the lens is removed by emulsification.
This operating technique presents the advantage, particularly with respect to the prior techniques, of necessitating only all incision of reduced dimension in the cornea with the aid of a knife precalibrated at 2 to 4 mm to introduce in the eye the instruments necessary for this ablation. It will be understood that it is interesting to have implants available which can be introduced in the eye through the incision made for the phako-emulsification operation, i.e. an incision whose length is of the order of 3 to 4 mm.
This is why new, so-called flexible intraocular implants have been developed. They present all optical part made of a flexible material which makes it possible to fold the optical part before introduction of the implant in the eye through the incision, the optical part resuming its initial shape after it has been placed in the eye. At the present time, two major types of products are used for producing the flexible optical part. These products are usually designated under the generic name, on the one hand, of flexible acrylics such as pHEMA and, on the other hand, of polysiloxane gel. These materials present the required optical properties and are, moreover, biocompatible.
The ablation of the lens leads to the deformation by contraction of the capsular sac and consequently to its opacification. The deformation of the capsular sac may lead to the disappearance of the circular symmetry of the capsular sac and therefore to the disturbance of the vision of the eye by alteration of the axes of symmetry of the optical system constituted by the capsular sac and the intraocular implant.
The haptic part of the intraocular implants participates in the maintaining of the initial shape of the capsular sac, in particular its circular periphery.
The phenomenon of deformation of the capsular sac is non-negligible in the case of the haptic part being constituted by two identical loops diametrally opposite and symmetrical to each other with respect to the optical center as, in that case, the zones of contact between the loops and the inner wall of the capsular sac are two limited zones which must support entirely the pressure exerted by the two loops.
Moreover, it should be noted that the deformation by contraction of the capsular sac brings about a risk of partial tear of the zonular ligament which retains the capsular sac.
This is why it has been sought to develop implants with a circular haptic part which will be in contact with the inner wall of the capsular sac over relatively extended zones.
A first solution consists in using a haptic part constituted by two identical, rigid loops symmetrical to each other with respect to a diameter of the optical part. This configuration imposes loops with a small diameter in order to avoid their deforming too much and to prevent an offcentering of the implant in the capsular sac. Loops of great length are also necessary to try to obtain a zone of contact which is as wide as possible. In that case, the problem of the contraction of the capsular sac brings about the risk of an intersection, i.e. an overlapping between the free ends of the loops, which might lead to the perforation of the sac.
A second solution consists in using a single annular loop attached to the periphery of the optical part bit a connecting arm. In the implants made in this configuration, either the haptic part is rigid and a minimum folded implant width call no longer be obtained, which was possible with two symmetrical rigid loops, or the haptic part is flexible and pliable, but the maintaining of the implant in the eye by this flexible haptic part is insufficient for the intraocular implant to remain centered in the capsular sac without collapsing.
An object of the present invention is to produce an intraocular implant which allows both a fold along a diameter of the optical part so as to obtain a width of folded implant of the order of 3 or 4 mm and a maintenance of the implant in the eye by the haptic part which avoids the deformation of the capsular sac and the centering or displacement of the optical part of the implant.
In order to attain this object, the intraocular implant according to the invention comprises a substantially circular optical part made of a first flexible material enabling it to be folded along a diameter and a rigid haptic part, this implant being characterized in that the haptic part comprises a substantially ring-shaped body, substantially concentric and coplanar to the optical part, said body presenting an opening, a first free end and a second connecting end, said body being made of a second material more rigid than the first material, and a base connecting in substantially radial manner the second end of the body of the haptic part to a peripheral zone of the optical part, said base being connected to the periphery of the optical part over a sufficient length corresponding to an angle b less than 180 degrees in order to avoid a movement of torsion of the optical part with respect to the haptic part.
It will thus be understood that the optical part which is flexible may be folded along a diameter which effectively allows the introduction of the implant in the eye through an incision of small dimension. On the other hand, the haptic part being substantially circular and rigid, one has a good hold of the capsular sac. Finally, thanks to the structure of the base of the haptic part, a displacement of the optical part with respect to the haptic part is avoided.
In order to introduce the implant the folded optical part is firstly made to penetrate in the incision then the base of the haptic part and finally the annular body is entered by rotation of the implant about all axis parallel to its optical axis preferably while maintaining the annular body substantially coplanar to the optical part.
According to a preferred embodiment, the intraocular implant is characterized in that the haptic part comprises a substantially ring-shaped body substantially concentric and coplanar to the optical part, said body at least presenting an opening, a first free end and a second connecting end, said body being made of a second material more rigid than the first material, and a base connecting in substantially radial manner the second end of the body of the haptic part to a peripheral zone of the optical part said base being made of the same first material and presenting a lateral zone comprising a rigid armature (30a) made with the second material which extends said body at least as far as the periphery of the optical part.
According to an essential characteristic of this embodiment of the invention, to allow folding of the implant with the obtaining of a minimum folded implant width while allowing a centered hold of the implant in the eye, it is provided that said base presents a first lateral zone comprising a first rigid armature made with the second material which extends said body at least as far as the periphery of the optical part and a second lateral zone comprising a second rigid armature made with the second material, not extending over the whole length of this second lateral zone and adjacent the optical part, with the result that there exists at least one diameter of the optical part which extends in the base of the haptic part without cutting said armatures.
It will be understood that the haptic part of the implant according to the invention comprises a sufficiently rigid, annular body in one piece allowing an efficient hold of the implant in the eye by a minimum deformation of this body, and a maximum distribution of the pressure exerted by the haptic part on the wall of the capsular sac.
It will likewise be understood that, according to the preferred embodiment, the bi-material structure of the base of the haptic part of the implant makes it possible, on the one hand, to fold the implant along a diameter of the optical part traversing this base so as to obtain a minimum folded implant width and, on the other hand, a minimum offcentering thanks to the rigid armatures of the lateral zones of the base of the haptic part which prevent too great a deformation of the latter.
Thanks to the first radial armature of the base of the haptic part which extends the annular body as far as the periphery of the optical part, the optical part is maintained centred about the optical axis of the eye. The second rigid armature and the flexible central part of the base of the haptic part increase, on the one hand, the mechanical bending strength of the first armature connecting the optical part to the annular body and, on the other hand, the moment of inertia of the base of the haptic part. Such increase in the moment of inertia avoids any pivoting about the diameter of the optical part which extends in the flexible central part of the base of the haptic part. In effect, such a pivoting would offset the optical axis of the implant with respect to the optical axis of the eye as they would no longer be parallel to one another and this would considerably spoil the optical correction contributed by the implant.
It should be noted that the implant according to the invention is not forcibly intended to be placed solely in the capsular sac; it may for example also be positioned in the posterior chamber of the eye, by bearing in the irido-ciliary groove (sulcus).
The invention will be more readily understood and the secondary characteristics and their advantages will appear in the course of the description of preferred embodiments given here in below by way of example.
It is understood that the description and the drawings are given only by way of descriptive and non-limiting example.